Ideal enantiomeric resolution (Preferential Enrichment) by recrystallization of a racemic compound. V: Relationship between Preferential Enrichment and crystal structures

The X-ray crystal structure of (±)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]ethyl]dimethylammonium p-nitrobenzenesulfonate [(±)-NNMe2], which shows the novel enantiomeric resolution phenomenon Preferential Enrichment, has been compared with that of (±)-[2-[4-(3-ethoxy-2-hydroxypropoxy) phenylcarbamoyl]ethyl]dimethylammonium p-toluenesulfonate [(±)-NTMe2], which does not show the phenomenon. The stable crystalline form of (±)-NNMe2 is a racemic compound, while that of (±)-NTMe2 is a mixed (disordered) crystal composed of the two enantiomers. The intermolecular hydrogen bonding mode in the crystal of (±)-NNMe2 was very different from that of (±)-NTMe2. Chirality 10:705–710, 1998.